Sertoli cells synthesize and secrete glycoproteins which interact with developing germinal cells in the male. It is the long-term goal of our research to ascertain the structure and function of these glycoproteins and thereby better define the role of Sertoli cells in spermatogenesis. Previous studies have concerned the role of testicular transferrin and sulfated glycoproteins 1 and 2. It was also shown that seminiferous tubules could be synchronized to contain only a few of the stages of the cycle of the seminiferous epithelium. The experiments in this proposal are designed to achieve 5 specific goals. First, the lipid binding properties of SGP-1 and SGP-2 will be investigated and the cloning of cDNA for SGP-1 will be completed. Second, cDNA probes will be constructed for previously uncharacterized secreted proteins from Sertoli cells. Third, the new cDNA probes will be used in studies designed to quantify the mRNA in cultured cells, hypophysectomized rats and vitamin A deficient rats. The mRNA's present at each stage of the cycle of the seminiferous epithelium will be quantified by in situ hybridization. Fourth, aspects of the model we have developed for transferrin action in the testis will be examined in detail. Specifically we will examine iron transport into germinal cells and the ontogeny of transferrin receptor mRNA and ferritin mRNA in germinal cells. Finally, the synchronized testis model system will be further defined and utilized to study stage- specific synthesis and secretion in Sertoli cells.